Currently, sublimation type thermal transfer recording method is known, wherein a thermal transfer sheet in which a sublimation type dye is supported on a substrate made of a plastic film or the like, and a thermal transfer image-receiving sheet in which a receiving layer is provided on a substrate made of a paper, a plastic film or the like are superposed to form a full color image. Since this method uses the sublimation type dye as a color material, this method excels in reproducibility and gradation of halftone, and thus, a full-color image can be clearly expressed as the original image on the image-receiving sheet. Therefore, this method has been applied in the color image formation for digital cameras, video recorders, computers or the like. Its image can rival silver halide photography with high quality.
As the thermal transfer image-receiving sheet to be used for the sublimation type thermal transfer recording method, a solvent type thermal transfer image-receiving sheet that has a solvent type dye receiving layer of the solvent system, and an aqueous type thermal transfer image-receiving sheet that has an aqueous dye receiving layer are known in the art. The solvent type thermal transfer receiving sheet excels in releasing property as compared with the aqueous type transfer receiving sheet. The solvent type thermal transfer receiving sheet, however, is poor in gloss of an image formed thereon, as compared with an image formed on the aqueous type thermal transfer receiving sheet. Therefore, in the field where high gloss is required for the image to be formed, there is a tendency that the thermal transfer image-receiving sheet of the aqueous type is preferred. Further, in view of problems such as the influence of treatment of waste liquid on the environment, there are increased tendency to use the aqueous type thermal transfer image-receiving sheet.
The aqueous type thermal transfer image-receiving sheet gives no adverse effect on the human body and the environment, and the aqueous type thermal transfer image-receiving sheet has an advantage of being able to impart a high gloss to the image formed thereon as compared with the solvent type thermal transfer image-receiving sheet. On the other hand, an aqueous type receiving layer shows a poor release ability with a dye layer, and thus, there are problems such that aqueous type receiving layer may cause fusion with the dye layer on printing, and a released mark may leave on a printed matter when peeling off the dye layer from the receiving layer, which are followed by a degression in the quality of printing.
Under such circumstances, various attempts for obtaining the thermal transfer sheet having an excellent releasing property to a thermal transfer image-receiving sheet have been made. For instance, in Patent Literature 1, a thermal transfer sheet which comprises a dye layer containing a silicone oil has been disclosed. Further, in Patent Literature 2, a thermal transfer sheet which comprises a dye layer containing a silicone-modified acrylic resin has been disclosed.
However, with respect to the thermal transfer sheet disclosed is in the Patent Literatures 1 and 2, and various thermal transfer sheets known to date, it has been not attained to give an release property which is even enough for a three-dimensional Y, M, and C printing at the highest gray-scale under a high temperature and high humidity environment. Thus, there have been many cases of leaving released marks on the printed matters. In particular, the released mark is likely to occur in the case of using the aqueous type thermal transfer image-receiving sheet.